Chapter 3 The Enhanced E-R Model

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Chapter 3 The Enhanced E-R Model

Jason C. H. Chen, Ph.D.Professor of MIS

School of Business AdministrationGonzaga UniversitySpokane, WA 99258

[email protected]

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#3-a (p.143)

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#3-b (p.143)

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#3-c (p.143)

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#3-d (p.143)

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#3-e (p.143)

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#9 (p.143)

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#9 (p.143)

Subtypes inside Supertypes Notation:

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#9 (p.143)

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#12 (p.144)Please note that the problem does not explicitly state that Skill is a multivalued attribute. Given the fact that examples in the text have skill as a multivalued attribute, we have made this assumption here also.

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#12 (p.144)Visio version

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#13 (p.144)Note: Again, we have assumed that Skill is a multivalued attribute.. Standard EER Notation:

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Subtypes inside Supertypes Notation:

#13 (p.144)

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#13 (p.144)

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#15 (p.144)

This Problem & Exercise has a different written scenario than a similar one in Chapter 2. The plural “requested judgment characteristics” in Chapter 2 is semantically different from this exercise’s “requested judgment characteristic” which results in the alternate model solution shown below. This may be useful to point out to students regarding the importance of paying attention to fine details while modeling data.

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#15 (p.145)Notes:1) Person Or Org attribute denotes Person or Organization type of Legal Entity. There is no reason to show Person and Organization as subtypes of Legal Entity, as there are no special attributes or relationships identified in the scenario.2) The same legal entity cannot be both a Plaintiff and Defendant in the same Case.3) Although DEFENDANT has no other unique attributes, it is required as a subtype to show the parties involved in a CASE. Further, the DEFENDANT subtype is necessary to show the Brought Against role that is necessary to defining the parties in a CASE.

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#16 (p.144)

Subtypes within Supertypes Notation:

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#16 (p.144)ER Notation

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#17 (p.145)

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#17 (p.145)Visio notation

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Subtypes within Supertypes Notation:

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#19 (p.145)Notes for EERD:1) Member Type values are Golf or Non-Golf.2) Social and Tennis members are considered Non-Golf members. A Social member has a Golf Rounds Limit of 2 and Tennis Courts? = N. A Tennis member has a Golf Rounds Limit of 4 and Tennis Courts?=Y. A Golf member has a Golf Rounds Limit of 999 and Tennis Courts?=Y.3) Golf members’ visits are tracked only if they bring a guest.4) If a Guest becomes a Member, then Guest records are archived out of the database.5) Member Date tracks the membership date of the Member.

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#21 (p.146)

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#21 (p.146)Notes:1) A PERSON, in his/her EMPLOYMENT, may hold multiple POSITIONs or not yet have an assigned POSITION (this is shown with the 0:M cardinality near POSITION from EMPLOYMENT).2) A POSITION might initially be unfilled, or over time, may be filled with multiple EMPLOYMENT instances of PERSONs (this is shown by the 0:M cardinality near EMPLOYMENT from POSITION).